Audio Research D70 mark1 + schematic

CDE's are fine provided the meet the capacitance and voltage requirements.

Now this D70 has got new filtercaps ! One thing I notice is that if the wipers on the biaspots should lose their contact
completely or partial there will be a currentrush in the powertubes . Judging from the position that these wipers have now with 65 mA through the new 6550:s ( Tungsol reissue ) it
is possible to add a resistor to each biaspot .... between the wiper and the side of the pot that have -47 VDC . I think this
resistor can have 120K or a bit less resistance. Kevin O´Connor describes this security - resistor in one of his books
about guitaramps . If the wiper should lose contact full bias-voltage will turn down ( choke ) the 65 mA current to a lower value ...... Wouldn´t it be possible to add this "mod " to a D70 ???? Thanks for some comment. Stewen

I've never seen a bias pot fail in a D70 or D115. They can get noisy however. It's 65mV as you are measuring across the resistor.

Hallo again ! I have been working with other items lately but today returned to the nice D70 . Measured the voltages at the
TIP 41 regulator circuit as the former advice pointed out as important . The correct values shall be 335VDC and 327VDC so
the difference is about 8VDC . I have 338 and 337 VDC !!!
The only component I´ve checked so far is the 1N914 diode which was OK. Can I check the zeners (2)? What component is
probably failed ? The IC ? The transistors is in a Darlington coupling . Think I can check them in the circuit,
right ? I mean , I don´t have to desolder to measure them ??
Well , thanks for any help , advice . Regards Stewen

TIP41 likely shorted out.
Collector should be about 340 and the output to the B+ for the 6922 should be 304V ( in the D115)

The D70 and D115 are hard to troubleshoot.